Structurally designed heterochain polymer derived porous carbons with high surface area for high-performance supercapacitors

Polyphosphazenes are considered as ideal precursors for nitrogen and/or phosphorus doped porous carbons for supercapacitor electrodes with high performances due to high phosphorus and nitrogen atoms content in their backbones. By adjusting the structure of the carbon-rich groups connected to each skeletal phosphorus atom, the structure of the corresponding carbons can effectively be tailored with appropriate content of heteroatoms and pores. Herein, we synthesized poly(naphthoxy/trifluoroethoxy)phosphazenes (PNTFPs) with different ratios of the two side groups. We envision that naphthoxylic side groups serve as “carbon source”, whereas trifluoroethoxylic side groups serve as “gas expansion agent” during processing heteroatoms-doped porous carbons. By controlling the carbonization temperature and the ratio of the two side groups on PNTFP, we have prepared nitrogen-doped porous carbons with a specific surface area of 2593 m²/g, and atomic nitrogen contents of 4.16%. The as-prepared material own specific capacitance up to 409F/g at current density of 0.1 A/g in a two-electrode system (542F/g at 0.1 A/g in three-electrode system) with capability of 259F/g at 20 A/g.